As a technique for allowing an observer to recognize a stereoscopic image, generally, a stereoscopic image display method based on binocular parallax using a difference between positions of the left eye and the right eye is used. This method is an application of the principle of stereogram that a three-dimensional stereoscopic image is recognized based on a difference between viewing methods in the brain by allowing the left eye and the right eye to visually recognize respectively-different two-dimensional images. As methods for displaying a stereoscopic image, there are a system using glasses and a naked-eye system not using glasses. As the naked-eye system, there are a two-eye system, a multiple eye system, and the like in accordance with the number of observer's viewpoints.
In order to represent a stereoscopic image based on the naked-eye system by using a two-dimensional display such as a general flat panel display, a method is used in which pixels displaying a left-eye image and a right-eye image are arranged in a two-dimensional display, an optical unit such as a lenticular lens having a cylindrical lens arranged therein or a parallax barrier having a slit-shaped light shielding pattern arranged therein is disposed between the two-dimensional display and an observer, and the left-eye image and the right-eye image on the screen are spatially separated so as to be visually recognized respectively by the left and right eyes.
In the technology described above, while an image is stereoscopically displayed on the screen of a two-dimensional display, a technology for displaying an image in which an object is represented as if it floats in the air has also been developed. For example, a method of stereoscopically displaying a three-dimensional image according to a volume scanning method has been proposed in which a two-dimensional display is arranged to be inclined with respect to the optical axis of an imaging optical system by using the imaging optical system such as a convex lens or a concave mirror, the two-dimensional image inclined with respect to the optical axis is moved through mirror scanning, and a three-dimensional image is formed by displaying a cross-section image of a display object on the two-dimensional display in synchronization with the movement of the two-dimensional image.
However, in the method described above, since a convex lens or a concave mirror is used as the imaging optical system, a distortion of the image occurs due to aberration of the convex lens or the concave mirror, and accordingly, the shape of a display object cannot be accurately reproduced. Regarding this problem, a method using a real mirror video imaging optical system such as an optical device including a plurality of dihedral corner reflectors each configured by two mirror surfaces as the imaging optical system has been proposed.
FIG. 1 is a perspective view that schematically illustrates a three-dimensional air video display device disclosed in Japanese Patent Application Laid-Open No. 2012-163702. FIG. 2A is a plane view schematically illustrating a dihedral corner reflector array that is a real mirror video imaging optical system of Japanese Patent Application Laid-Open No. 2012-163702, and FIG. 2B is a partial enlarged diagram of a portion A. For example, in Japanese Patent Application Laid-Open No. 2012-163702, as illustrated in FIGS. 1, 2A, and 2B, a three-dimensional air video display device has been disclosed in which at least two real mirror video imaging optical systems that can form real images of a projection object at plane-symmetrical positions with respect to one geometric plane that becomes a plane of symmetry are arranged to be aligned, projection objects are arranged in correspondence with the imaging optical systems, and a real mirror video of a corresponding projection object that is formed by a right-eye imaging optical system that is one of the above-described real mirror video imaging optical systems arranged on the relatively left side and a real mirror video of a corresponding projection object that is formed by a left-eye imaging optical system that is one of the above-described real mirror video imaging optical systems arranged on the relatively right side are displayed to overlap at a same position.
FIG. 3 is a perspective view that schematically illustrates a volume scanning-type three-dimensional air video display device according to Japanese Patent Application Laid-Open No. 2013-080227.
FIGS. 4A and 4B are diagrams that schematically illustrate an image formation pattern according to a dihedral corner reflector array that is a real mirror video imaging optical system of Japanese Patent Application Laid-Open No. 2013-080227. In Japanese Patent Application Laid-Open No. 2013-080227, as illustrated in FIGS. 3, 4A, and 4B, a volume scanning-type three-dimensional air video display device has been disclosed which includes: a real mirror video imaging optical system capable of forming a real image of a projection object at plane-symmetrical positions with respect to one geometric plane that becomes a plane of symmetry as mirror videos; a display that is arranged on the lower face side of the plane of symmetry and includes a display surface displaying a video as the projection object; and a drive unit that operates the display to make a motion including a component of a direction perpendicular to the display surface and, by changing a video displayed on the display surface in synchronization with the operation of the display according to the drive unit, forms the video as a stereoscopic video in a space disposed on the upper face side of the plane of symmetry.
As above, by combining the two-dimensional display and the real mirror video imaging optical system 91 as illustrated in FIGS. 2A and 2B or 4A and 4B and by arranging two-dimensional displays corresponding to viewpoints as in Japanese Patent Application Laid-Open No. 2012-163702 or moving the two-dimensional display as in Japanese Patent Application Laid-Open No. 2013-080227, an air floating image can be displayed. However, in the configuration disclosed in Japanese Patent Application Laid-Open No. 2012-163702, as illustrated in FIG. 1, a two-dimensional display used for displaying a projection object 92 corresponding to the number of viewpoints is required, and, in the configuration disclosed in Japanese Patent Application Laid-Open No. 2013-080227, as illustrated in FIG. 3, the drive unit 95 that moves the two-dimensional display 94 is required. Accordingly, there is a problem in that the size of the device becomes large.
For this problem, a method of displaying an air floating image by combining a spatial imaging device such as the real mirror video imaging optical system described above with a display (a so-called naked-eye type 3D display) in which an optical unit such as a lenticular lens is arranged in a two-dimensional display may be considered. However, in the case of such a configuration, a new problem that a 3D normal viewing area (an area in which the depth of a 3D object is correctly displayed) and a 3D reverse viewing area (an area in which the depth of a 3D object is reversed) alternately appear in the air floating image occurs.
The present invention is in consideration of the problems described above, and a main object thereof is to provide a stereoscopic display device and a parallax image correcting method capable of avoiding a problem that a 3D normal viewing area and a 3D reverse viewing area appear in an air floating image in a configuration combining a naked-eye type 3D display and a spatial imaging device.